There is no Karma or reputation loss for killing either of them and taking their hats, but they do not drop the key or code to the safe when they die. The Courier must either pass the Speech check of 55 or pick the Very Hard lock that requires 100 Lockpick if they wish to open the safe and retrieve Vance's 9mm submachine gun.

Regardless of the fact that both she and Sammy state the only gun they possess is Vance's gun, if she becomes hostile to the Courier she will equip a separate submachine gun. Also the couple claims to be very tough, yet if the Courier kills Sammy and then holsters their weapon, Pauline will not attack.